Diesel engine use for passenger car applications is increasing due to the benefit of better fuel economy. Further, gasoline engines are increasing compression ratios to improve the fuel efficiency. As a result, diesel and gasoline engine accessory drive systems have to overcome the vibrations of greater magnitude from crankshafts due to above mentioned changes in engines.
Due to increased crankshaft vibration plus high acceleration/deceleration rates and high alternator inertia the engine accessory drive system is often experiencing belt chirp noise due to belt slip. This will also reduce the belt operating life.
Crankshaft isolators/decouplers and alternator decouplers/isolators have been widely used for engines with high angular vibration to filter out vibration in engine operation speed range and to also control belt chirp.
Representative of the art is U.S. Ser. No. 13/541,216 which discloses an isolator decoupler having a pulley temporarily engagable with an end of the wrap spring one way clutch in an unwinding direction whereby a temporary contact between the wrap spring one way clutch end and the pulley will temporarily diminish the frictional engagement of the wrap spring one way clutch from the shaft.
What is needed is an isolating decoupler comprising a wrap spring engaged between the carrier and the shaft, the wrap spring comprising a cylindrical inner portion and a planar outer portion connected by a tapered portion, and the inner portion frictionally engaged with the shaft in a winding direction. The present invention meets this need.